In recent years, hard disk drives have been required to have even greater storage capacity and faster operating speed. In this regard, it has become more important to maintain cleanliness within the hard disk drive. As a hard disk drive, a structure is known in which an actuator (arm) having a magnetic head at the tip thereof is rotatably supported by a pivot assembly bearing device (see Japanese Unexamined Patent Application Publication No. 2011-220427).
The pivot assembly bearing device includes a rolling bearing, and a lubricant is used in the rolling bearing. Here, there may be a case in which this lubricant causes a negative effect on the cleanliness of the internal space of the hard disk drive. To solve this problem, Japanese Unexamined Patent Application Publication No. 2008-69920 discloses a structure in which a flange is formed on a shaft, and a labyrinth seal to prevent leakage of lubricant is formed by a gap between an outer circumferential surface of this flange and housing.
The structure of the labyrinth seal in Japanese Unexamined Patent Application Publication No. 2008-69920 cannot sufficiently prevent the lubricant from leaking because the length of the gap extending along a leak path of the lubricant is short and the extending direction of the leak path is in only one direction. In view of such circumstances, an object of the present invention is to prevent the lubricant from leaking.